In this article, our National Technical Lead for Food Safety and Animal Welfare, Ester Benguerel, shares her thoughts on the impact CO₂ pig stunning has on animal welfare.

Every year, millions of pigs in the UK are stunned using high-concentration CO₂ before slaughter. Carbon Dioxide is currently a perfectly legal stunning method according to both UK and EU legislation and in the past this was considered to be one of the best options available. While the method is efficient, evidence shows it comes at a significant cost to animal welfare, a cost that is entirely avoidable given current stunning options which are far better for animal welfare.

The Animal Welfare Committee (AWC)’s recent opinion concludes that high-concentration carbon dioxide (CO₂) stunning causes avoidable pain, intense distress and breathlessness in pigs before they lose consciousness. The Committee recommends moving away from CO₂ and introducing more humane alternatives.

Carbon dioxide is a powerful respiratory irritant. When inhaled, it interacts with the mucous membranes, leading to hypercapnia and acidosis. Essentially, a buildup of carbon dioxide in the bloodstream. This triggers gasping, burning sensations in the airways and intense respiratory distress, causing a feeling known as air hunger, the desperate need to breathe.

To put this into perspective, imagine holding your breath for as long as you can. Within seconds, your body begins to panic, forcing you to inhale. Now imagine that your first breath burns your nose and throat, and the next one brings no relief, only more pain and suffocation. That overwhelming sense of panic and the inability to breathe properly is what conscious pigs experience during CO₂ stunning. And remember, nobody tells the pig to take an enormous breath before it goes in.

At concentrations above 80–90%, pigs exhibit frantic escape attempts, gasping and vocalisations, unmistakable signs of fear, pain and extreme breathlessness. These are not isolated reactions; they are consistent physiological and behavioural responses that occur every time CO₂ is used. Because CO₂ stunning is so widespread, millions of animals experience avoidable suffering each year.

Alternatives exist, though they require careful implementation. Inert gases like Argon or Nitrogen can render pigs unconscious without the respiratory irritation associated with CO₂, but ensuring consistency, managing costs and maintaining meat quality are ongoing challenges. Electrical stunning delivers immediate unconsciousness; however it requires good structural design for animal handling and skilled operators in place. Low Atmospheric Pressure Stunning (LAPS) also shows promise, but it still requires further validation before widespread use.

The Animal Welfare Committee recommends a phased transition from CO₂, supported by investment in research, development, validation and industry guidance to scale humane solutions effectively.

The evidence is clear, CO₂ stunning causes unnecessary and predictable suffering, and better alternatives exist. Unfortunately, this method continues to be legal, so we are forced to accept this in daily practice. However, transitioning to more humane methods is not just ethically right, it aligns with animal welfare legislation, strengthens public trust in the food system, and would position the UK as a leader in responsible farming practices.

If you care about animal welfare, the conversation is no longer about if we should move away from CO₂, but how quickly we can implement safer, more humane alternatives.

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